Telephone-exchange system



R. s. WILBUR TELEPHONE EXCHANGE SYSTEM Filed Dec. 14 1920 s Sheets-Sheet 1 03 S /M venfan,

fiay 5. M'lbul March-17, 1925.

$29,918 R. s. WIL BUR 'rELEfHoNE EXCHANGE SYSTEM Filed Dec 14, 1920 8 Sheets-Shedt 2 //4 van /0/ Ray 5. Wi/bw. by

Much 17, 1925. I 1,529,978

R. S. WILBUR ransom Excxumez SYSTEI Filed Dec 14, 1920 8 Sheets-Sheet 3 y @JRXHM v s. WILBUR TELEPHONE EXCHANGE SYSTEM Filed Dec. 14, 1920 8 Sheets-Sheet 6 iiiiil 1 WWW: Ray 5. h f/hur 81mm? My.

Patented Mar. 17, 1925.

UNITED STATES PATENT OFFICE.

RAY SETH WILBUR, or LYNDHURST, JERSEY, essrenon 'ro WESTERN nnnornrc COMPANY, mconronnrrnn, or new roan, n. a conrona'rron or new YORK.

TELEPHONE-El i Application filed December To (6% whom. it may concern:

Be it known that I, RAY. i). lVILBUma citizen of the Umted'States of America, re-

siding at Lyndhurst, in the county of Bergen, State of New Jersey, have invented certain new and useful Improvements in 'lelephone-Enchange Systems, of which the following is a full, clear, concise, and exact description. I I

This invention relates to telephone exchange systems and more particularly to such systems in which toll connections are established between exchanges by means of machine switching equipment controlled over toll lines.

Objects of the invention are to provide in'iproved methods and means for enabling an operator at one exchange to extend a connection over a toll line to a subscribers station at a distant exchange by means of automatic switching mechanism and to provide the operator with complete supervision over such a connection. v

Another object of the invention is to pro vide suitable circuit arrangementsin a system of this nature so that-traffic may be handled in either direction over the same circuit.

Further objects are to improve the supervision over long lines and to translate co1nbinations of equal numbers of current impulses into combinations of varying numbers of current impulses.

To attain the objects of the invention means are provided whereby, the building up of a connection from the originating exchange to the subscribers station at the distant exchange, the application of ringing current tothe called line,'various supervisory signals at the originating exchange and the release of the connection are controlled by means of a plurality of relatively high frequency current-s transmitted over the toll line.

More specifically the invention contemplates the provision of impulse transmitting means, whereby for each digit of a nuniber desired, a plurality of impulses of relative ly high frequency currents are transmitted over the toll line to an impulse receiving device, which filters, rectifies and translates these impulses into direct current impulses corresponding to a digit key depressed at the operators position. A plurality of sources CHANGE SYSTEM.

of current of different frequencies at the.

combinations of frequencies for the different signals transmitted.

These and other objects of the invention will be more readily understood by refer-' ence to the accompanying drawings, which when arranged as shown in I ig. 9 of, the drawings illustrate one embodiment of the invention. Fig. 1 shows cord circuit at an originating toll operatons position a ciated with the toll operators position in any well-known manner, and the calling jack of one of the. toll trunks appearing bcfore the toll operators position; Fig. 2 shows apparatus individual to theoutgo-ing end of a toll trunk line, a receiving circuit R and a switching device I), hereinrtermed a distributor, for associating the receiving circuit It with the toll line; Fig. 3 shows apparatus individual to the incoming end of the toll trunk line, a receiving circuit R a switching device 1), herein termeda distributor, for associatingthe receiving circuit R with the toll line, and a line finder switch LFS for extending the tollline; Fig. t includes a link circuit for extending the toll line, and a switching device RSF for associating the receiving and translating circuit R with the trunlrline; Fig. 5 shows a receiving and translating circuit R for receiving relatively high frequency currents and translating them into direct calling subscribers line which may be assocuit; and Fig. 8 shows a connector circuit and the substation LL of a called subscrihers line terminating therein.

in general the system functions in the following n'ianner: A' subscriber at station HH, desiring aconnection with asubscriber LL at a distant exchange, first obtains a connection through the position of the usual A or answering operator to a toll switching trunk, whereby the connection is extended to the toll operators position. The toll operator answers with an idle cord AA and after ascertaining the number desired at the distant exchange, extends the connection by means of her calling plug over an idle toll line extending to the desired distant exchange.

In response to the seizure of the toll line the cord selector switch CS, associated with the cord circuit, will operate to associate an idle impulse sender S with the cord circuit AA, and a relay, associated with the trunk circuit, will operate to impress 900 cycle current on the outgoing end of the toll line so that when the distributor D associated with the distant end of the toll line, engages the contacts of the seized line, the 900 cycle current will actuate relays 1n the receiving circuit R causing the operation of the toll line relay of the seized toll line'at the distant oilice.

The line relay in operating causes the switch LFS to be operated, which in turn causes the operation of the finder switch RSF, thereby extending the toll line to the receiving circuit R As soon as the line finder switch LFS operates to extend the toll line, 1300 cycle current at the distant exchange is impressed upon the toll line conductors, which, in conjunction with the 900 cycle current at the originating exchange, operates relays 1n the 1 receiving circuit R, which operate the sender switch SW The 900 and 1300 cycle currents are thereupon disconnected from the toll line and as soon as the number desired by the calling subscriber has been set up by the operator on the sender-S, a plurality of impulses of high frequency current wlll be transmitted over the toll line to the receiving circuit R for each digit of the desired number. The receiving circuit R is common to a plurality of toll lines and serves to translate and repeat impulses delivered thereto.

The sets of impulses transmitted by the distributor D corresponding to the depressed keys of the sender S, are filtered and rectified at the receiving circuit R causing the switches F8 F8 and FS to be operated. Each time set of impulses 1s transmitted from the sender to the receiving circuit R certain relays associated with one or more of the switches F8 FS and F5 are operated to cause the operation of a particular counting relay, said counting relay corresponding to the digit represented by the depressed key of the sender S.

The counting switches CT, CT? and CT are then successively operated, causing in turn the successive operation of as many of the pulsing relays associated with the distributor D as keys have been depressed at the sender S. The distributor D in rotating, will transmit impulses over impulse conductor 699 to the impulse relay 700 associated withthe selector SL. In response to the actuation of the impulse relay, selector switch SL and connector switch CC will be set upon the terminals of the desired line. As soon as the last impulse is delivered by the distributor D, the switch RSF is operated, thereby freeing the receiving circuit R and restoring all apparatus in said re ceiving circuit to normal position.

If the desired line is idle, 900 and 1100 cycle current will be automatically impressed upon the toll line and will be received by the receiving circuit R, operating relays therein which will cause the supervisory lamp in the cord circuit to light, indicating that the ringing signal may be transmitted.

1n transmitting a ringing signal, the operator depresses the ringing key, thereby simultaneously applying 900 and 1100 cycle current to the line conductors, which currents are received by the receiving circuit R Relays of the receiving circuit R thereupon operate and cause ringing current to be impressed upon the line of the called subscriber for a period determined by the time required for the distributor associated therewith to operate through two cycles. If it is desired that ringing current be continued, it is necessary for the operator to maintain the key actuated for the desired period.

Then the called party answers, 900v and 1800 cycle currents will be connected simultaneously to the toll line for a period representing the time required for two cycles of the distributor. These currents are received by the receiving circuit R, causing the operation of relays therein, which in turn cause the extinguishment of the supervisory lamp. lVhen the called subscriber restores the receiver to the switch hook, 900 and 1100 cycle currents are simultaneously connected to the toll line for a period representing the time of two cycles of the distributor D. These currents are received in the receiving circuit R and cause the operation of relays therein, which in turn cause the supervisory lamp to be lighted, indicating to the operator that conversation has ceased.

If the called subscriber flashes, 1100 and 1300 cycle currents will be connected simultaneously to the toll line, causing the connection of an interrupter to the sleeve circuit of the cord circuit AA, which will cause the supervisory lamp of the operators cord circuit to be flashed. The operator noting the flashing signal mayactuate her listen ing key "whereupon the flashing signal will be disconnected. If the called line is busy, a busy signal will be transmitted to the operator.

As the toll line is adapted for use as a avengers for establishing a connection from theorigi na-tlng exchange tothe distant exchange only, has been shown complete. The cord selector switch GS, sender. switch Si/V and sender S at the toll operators position at the second exchange may be similar to cor.- responding apparatus shownin Fig: 1 of the drawings, and the apparatus for conr pleting a connection originated atthe operators position at the distant exchange has been represented in- Fig. 2 by a blank rectangle VA, itbeing understood that the apparatus contained within the rectangle is identicalwith that fully disclosed in Figs; 4 to 8-inclusive, and withinv the dotted lines inFig. S ot the drawings.

Devices" for filtering and converting fil tered currents into: unidirectional currents are well known in the art and such devices have therefore been indicated simply by rectanglesz These devices maybe of the general type disclosed: in Patent No. 13261 290 01 Apr-iii 2, 1918 to P. Rainey. The

apparatus herein termed distributors may be o f any sultabl'e desigir 1n which thecontacts thereof are suitably insulatedand are -wiped over by constantly rotating brushes.

The operation ot the system will lee-better understood: from a detailed description thereof. Since the line of a calling subscriber such as'HHl' may beextended to the operator at the originating exchange in a v manner well known in the art, the description of; such an extension Wlll be omitted.

It will be assumed. that the operator at the 202 over a path: extending. from ground,

winding 01 relay E202, sleeves of jack 111 1 and plug 110, and windings of relays 101 and 103 to grounded battery. Although current also passes through relay 103 at this time, said relay 103' does; not operate since it is of the marginal type. Relay 101 in operating completes a'circuit for relays 104:

and 105 over a. path extending from ground, armature and front contact of relay 101 and thence in parallel, one path extending through thewinding of relay 10% togrounded battery and the other path extending through the left hand armature and back contact 015 relay 107 and the winding of relay 105 to grounded battery. Relay 10.5 thereupon operates, thereby disconnecting the answering end of the cord circuit AA To simfrom the calling end and connectingcontact s oh the cord finder switch OS to the calling plug; 110 of the cord circuit. Relay 10% in operating'completes a circuit for-,t'he' operation ot'relay106 over a path extending from ground right-hand arn'iatureand basic contact of relay 107, armature and front contact otrelay 190d, normal contact 199' and: brush125 of cord finder switch (0S3 winding of relay- 106'and back: contact and inner left hand armature oi relay 108 toground'ed battery.

As soonas relay 1 06 operates, acircuit is completed for the stepping magnet 126 of the switch OS over a pathv extending from grounded batte1-y,:w-inding-', armature and back contact ofniagnet' 126; right hand armature and front contact of relay 106 brush 1 25 and contact 1 99' of: switch CS; front contact and armature of relay 1 04 and back contact and right hand armatureof relay 107 to ground. Magnet 126tihereupon: operates and continues to operate to move the brushes 120. to 1 25 inclusive of the switch CS over its associated: contacts; as long asbrush 125 engagesbusy contacts or contacts having ground potential thereom As soon as brush 125 reaches a contact of a calling circuit or acontact' having no potential thereon relay 106- releases to open: the stepping circuit. Relay 106 is preferably slow to release so as to maintain the circuit of magnet 126 closed" during the stepping operation. In the present instance, it is assumed that thecorch circuit an is connected to the switch OS sothat the relay 108 operates over a path extending from grounded battery, winding; and right hand normal contactsof relay 108, left hand normal contacts 0t relay 106, brush 12d and contact 134 of switch CS, and back contact and right hand armature of relay 107 to ground. Relay 1 08, in operating, locks up through its right hand normal contacts and through brush 12 1 and contact 134.- of switcl'r CS to ground at the back' contact and right hand armature oi relay 107. Relay 108, in attracting its inn'er l'ett hand armature, removes battery from the winding" oirelay 1'06; and in attracting its intermediate left hand armature, connects ground. to contact 135 of the switch CS for the purpose of rendering the selected set 013 contacts busy. At the outer left hand arn'iature and front contact ofrelay 108*, tlie conductor 128 is extended to: the brush 14 1 or: the sender switch SV.

When the brush of the switch CS moves into its second position;, an obvious circuit is closed for the lighting of lamp signal 136 which serves not only as'aguard signal but to indicate the particular sender which has beensel'ected if a. plurality ct cord selectors have been employed. Itv will be obvious that conductors such as 127 and 128 leading to the cord AA may be multipled to the contacts of one or more other switches similar to CS with each of which a sender may be associated.

W'hen relay 202 of the toll trunk line circuit operates, a circuit for relays 209 and 210 is completed over a path extending from ground, armature and front contact of relay 202 and thence in parallel, one path ex tending through the left hand armature and back contact of relay 216 and the winding of relay 209 to grounded battery, and the other path extending through the winding of relay 210 to grounded battery. Relay 209, in attracting its left hand armatures, renders the outgoing end of the toll line circuit discontinuous and connects 900 cycle current to the line circuit. When the .distributor D shown in Fig. 3 of the drawings, engages contacts of this line, the 900 cycle current flows into the receiving circuit R The 900 cycle current flows into the receiving circuit R associated with the dis tributor D but it will not produce any effeet on the line relay at the originating exchange due to the circuit for said line relay being open at the contacts of relay 250, the operation of which will be later described. Relay 210 in operating completes a circuit for relays225, 241 and 250 over a path extending from ground, inner right hand armature and front contact of relay 210, thence in parallel, one path extending through the left hand normal contacts and winding of relay 225 to grounded battery, and the other path extending through the windings of relays 241 and 250 in series to grounded battery. Relay 225, in operating, locks up through its left hand alternate contacts to ground at the outer left hand armature and back contact of relay 240. Relay 225 in operating also prepares a circuit for the application of 1100 and 1300 cycle current to the line conductors, the function of whichis to cause the release of the connection as will be later described. Relay 241, in operating, connects the relays 214, 240, and224 in operative relationship with the distributor D and opens the conductors of the line circuit extending to a line finder (not shown) associated with the outgoing end of the toll line similar to LFS, shown in Fig. 3 of the drawings. Relay 250, in operating, connects the relays 201 and 220 in operative relationship with the distributor -D.

\Vhen the 900 cycle current is connected to the line circuit, relay 301 of the receiving circuit R operates by induced current from the source 230, over a path extending from grounded battery, armature and back contact of relay 307, winding of relay 301 through the 900 cycle frequently filter 300 brush 341 and contact 361 of the distributor D right hand winding of repeating .coil 380, contact 360 and brush 340 of the distributor D and through the 900 cycle filter 300?,to ground. Relay 301, in operating, closes a circuit for the operation of line relay 310, over a path extending from grounded battery, through the winding and the left hand normal contacts of line relay 310, right hand normal contacts of cutoff relay 311, back contact and outer right hand armature of relay 315, contact 366 and brush 346 of the distributor D back contact and lefthand armature of relay 303, left hand armature and back contact of relay 302, and left hand armature and front contact of relay 301 to ground. Relay 310, in operating locks through its left hand alternate contacts and through the'back contact and left hand armature of cutoff relay 311 to ground. Relay 310, in operating, also places ground, through its inner right hand at ternate contacts on contacts 375 and 377 of a eration of only one switch is described here-- As soon as ground is placed on the contact 377 of switch LFS, relay 404 operates over a path extending from grounded battery, left hand armature and back contact of relay 405, winding of relay 404, brush 336 and contact 377 of switch LFS and front contact and inner right hand arma-' ture of relay 310 to ground. Relay 404,

in operating, completes a circuit for stepping magnet 390 for the switch LFS overv a path extending from groi'inded battery, winding and armature and back contact of magnet 390, left hand armature and front contact of relay 404, brush 335 and contact 375 of switch LFS, and front contact and inner right hand armature of relay 310 to ground.

Under the control of motor magnet 390, the brushes of the switch LFS step to the line taken for use, whereupon relay 404 releases due to the opening of its circuit at the back contact and outer right hand armature of line relay 310, thereby opening the operating circuit for magnet 390, and relay 405 then operates in series with the cutelf relay 311 over a path extending from grounded battery, armature and back contact of relay 312, winding of relay 311, contact 374 and brush 334 of switch LFS, right hand armature and back contact of relay 404, right and normal contacts and winding of relay 405 to grounded battery.

311.0ver the circuit just traced.

Relay 405 then locksthrough its right hand alternate contacts in 'SQIlBSWltlICLlt-Ofi relay Relay 311, in "attracting its left .hand armature, opens thelocking'circuit for line relay 310 Whereupon said line relay 310 releases. Relay 310 in releasing places ground upon contact 378 for the purpose of rendering the .toll line busy. Relay 405 in operating completes va armature completes a circuit for relay 407 over a path extending from grounded battery, winding of relay 407, left hand armature and front contact of relay 406 and left hand normal contacts of relay 409 to ground.

. link circuit is found.

Relay 407, in attracting its right hand armatures, interrupts the continuity of the link circuit and connects 1300 cycle current to the line and in attracting its left hand armature completes a circuit for the energization of relay .408 over a path extending-from ground, front contact and left-hand armature of relay 407, leftehand normal, contacts and Winding of relay 408 to grounded battery. Relay 408thereupon operates and locks up to ground through the left-hand armature and back contact of relay 409. Relay 408 in operating completes a circuit for the operation of relay 410 over a path extending from ground, outer right-hand armature and front contact of relay 408, contact 466 .and'brush 462 of the switch 'RSF, Winding of relay 410, and back contact and righthand armature of relay411 to grounded battery. Relay 410 in operating completes a circuit for stepping magnet 401 over a path extending from grounded battery, Winding, armature and back contact of magnet 401, armature and front contact of) relay 410, brush 463 and contact 468 of switch RSF, and front contact and outer right hand armature of relay 408 to ground.

Under the control of magnet 401, the brushes of the switch RSF, are, moved over their associated contacts until the selected As soon as the selected link circuit is found, relays 411 and 412 operate over. a path extending from ground, Winding ofrclay 412, contact 444 and brush 440 of the switch RSF, outer right-handarmatureandbackcontact of relay 410, lefthand normal contacts and winding of relay 411,,and outergleft-handarmature and front contact of;re la.y 408 to grounded battery. Relays ,411 and 412 then look up, over a circuitincluding thefllefthand alternate contacts of IBlay.s411, under control of relay operates.

408. Relay 410 releasesand opensthecircuit of magnet 401 as soon asrelay 411 Relay 411 in operating also completes a circuit'at its right-handalternate contacts for :the energization of relay 413, thereby connecting the receiving circuit R to the brushes ofthe switch RSF.

As soon as the selected link circuit is found, relay 414 operates over a path 6X". tending from grounded battery, Winding of relay 414, contact 471 and brush 461 of switch RSF, conductor 598 and back contact and left-hand armature of relay 662 to ground. Relay 414 in attracting its lefthand armature, completes .an obvious circuit for relay 409, and in attracting its right-hand armature completes a circuit over a path eXtendingfrom grounded battery,

right-hand farinature and front contact of relay 414, contact 470, and brush 460 of switch RSF, Winding and left-hand alternate contacts of relay 411, brush 440 and 7' contact .444 of switch RSF and Winding of relay 412 to groundfor maintaining relays 411 and 412 energized. As soon as relay.

409 attracts itsle'ft hand armature, it releases relay 407 and opens the locking circuit for relay 408, whereupon said relay 408 releases, thereby opening the original energizing and locking circuit for relays 411 and .412. Relay 409 in attracting its righthand armature, locks up overapathinclud ing the front contact andleft hand armature of relay 405.

l/Vhen relay 407 operated, 1300 cyele cur- {rent Was projected overwthetoll line and receivedat the receiving circuit 1% operating relay 262 therein. It .Wlll be noted that re.- lay. 209, which 'WhOD operatedJc-o-nnects 900 cycle current to the line. is also operated at. this time, so that 900 cycle current is also projected over the line circuit and will be I'QCBIVGCl by the receivnig circultfi operatlng relay 264 therein. The 900 and 1300 cycle currents :passing into the receiving clrcu t R do not affect the distant exchange because relay 313 is not operated. Relay264 is operated over a path extending from grounded battery, armature and back contact of relay 265, Windingof relay 264, throughthe 900 cycle filter 200 brush285 and contact275 of distributonD, outer left h and armature and front contact of relay 209, ,through the source 230 of 900 cycle current front contact and innerleft hand armature of relay 209,: contact 276 and brush 286 of distributor D, through the 900 cycle filter j 200f to ground. The circuit for the fenergization of relay 262 maybe traced as follows: grounded battery, armature andbackcontactlof relay 265, \vindingof relay 262, through the l 300 cycle frequency {filter 200f ,brush and contact 275 of distributorQD, throughgthe left-hand Winding of repeating pcoil ,290,

contact .276 andhrush 2860f distributorfD,

through the 1300 cycle frequency filter 200 to ground, current from the 1300 cycle source 450 having been transmitted over an obvious path tothe right-hand winding of repeating coil 290 and having been induced into the left-hand winding. Relays 264 and 262 in operating complete a circuit for the energi- Zation of relay 115 of the sender switch Sl V over a path extending from ground, front contact and right-hand armature of relay 264, back contact and right-hand armature 'of relay 268, right-hand armature and front cuit for the motor magnet 102 to advance the brushes of the sender switch SlV one step. This circuit may be traced as follows: ground, armature and front contact of relay 115, contact 169 and brush 144 of sender switch SW, armature, back contact and winding of motor magnet 102 to grounded battery. Relay 214 also operated in series with relay 115 over the circuit previously traced for the energization of relay 115.

Relay 214 in operating locks through its alternate contacts and provides a holding circuit through its outer right-hand contacts for relay 209. In attracting its left-hand armature, relay 214 completes an obvious circuit for relay 21.6. Relay 216 thereupon operates and looks over a path extending from grounded battery, winding, front contact and left-hand armature of relay 216, and front contact and right-hand armature of relay 202 to ground.

As soon as the brushes of the sender switch SlV were moved one step, the energizing circuit for relays 214 and 115 was opened thereby causing the release of said relays. Relay 214 in retracting its outer right-hand armature interrupts the holding circuit for relay 209, whereupon said relay 209 retracts its armature thereby rendering the conductors of the line circuit continuous and disconnecting 900 cycle current from the line.

It will be assumed that as soon as the operator inserted plug110 of the cord circuit AA into the ack 111 of the link circuit, she operated keys of the impulse sender S corresponding to the digits representing the nun1- ber of the desired subscriber at the dist-ant As soon as the key for the hundreds digit is motor magnet 102, over a path extending from ground, contact 192 and brush 1.91 of distributor D outer right-hand contacts of the hundreds digit key 1, strapped contacts associated with brush 142 and brush 142 of switch SWV and winding of magnet 102 to advance the brushes 140 to 144 in elusive one step.

The constantly rotating distributor D will then cause three closely succeeding impulses of 900 cycle current to be sent over the line, thereby causing the operation 01' the relay 520 of the receiving circuit R in the following manner: current from the source of 900 cycle traverses contacts 190 and brush 181 of distributor D left-hand contacts of hundreds key 1, contact 161 and brush 140 of sender switch SW, conductor 149, brush 121 and contact 131 of cord finder switch CS, front contact and outer armature of relay 105, rings of plug 110 and jack 111, back contact and inner lefthand armature of relay 209, left-hand winding of repeating coil 290, outer left-hand armature and back contact of relay 209, tips of jack 111 andplug 110, inner armature and front contact of relay 105, contact 132 and brush 122 of cord finder switch US, conductor 128, front contact and outer left-hand armature of relay 108, brush 141 and contact 164 of sender switch SlV, righthand contacts of hundreds key 1, to source of 900 cycle ringing current; the current through the left-hand winding of repeating cell 290 will be induced into the right-hand winding of repeating coil 290 and will then flow over the conductors 291 and 292 through the left-hand windin of the repeating coil 380 at the distant oihce, thereby inducing a corresponding current in the right-hand winding of the repeating coil 360; the current induced into the right-hand winding of repeating coil 380 will cause the opera tion of relay 520 over a path extending from grounded battery, winding of relay 520, through the 900 cycle frequency filter 500/", conductor 547, inner armature and front contact of relay 413, brush 441 and COllTilOt- 445 of switch RSF, front contact and inner right-hand armature of relay 412, conductor 493, inner right-hand armature and front contact of relay 406, conductor 491, back contact and inner right-hand armature of relay 407. brush 332 and contact 372 of switch LFS, back contact and inner righthand armature of relay 318, through the right-hand winding of repeating coil 380,

outer right-hand armatureand back contact of relay 313, contact 371 and brush 331 of switch LFS, outer right-hand armature and back contact of relay 407, conductor 490,. front contact and outer right-hand armature armature of relay 516. to ground.

601 in operating locks temporarily ;under .gized three times, therchy of relay e06, conductor 4 92, intermediate rightdiand armature :and trout contactuoi relay e12, contact H6 and brush 4512 of switch RSF, front contact and muterarma- .ture of relay 413, conductor 5 18, :through the 900 cycle frequency filter 500; to ground.

} In response'to "the three impulses transmitted to the relay 520,;1nagnet associated with :the switch IFS will be enercausing the brushes 530 to 5232 inclusive to be \moved three steps over :their associated iterniinal banks. In response :to the first impulse transmitted to relay 520, relay 521energizes .orcr an obvious circuit. This relay is preferably ot' the slow+to-release type and retains its armature attractedduringthe-transmission of the remaining ninpulscs ot the series to relay 520. After the last impulse ot'the series has been transmitted to relay 520, relay 521 releases, tl1er'eby causing the.

o iaeration of countin rela 601 over-a iath L l) extending "from grounded battery, winding andright-handnornialcontacts otrclay601,

* -conductor 590, contact and brush 532 of switch F8 arl'nature' and baok contact of relay 521 and baek contaet and right-hand Relay control of relay .62lrandzcompletes acircuit "tor theenergization of relay 516 over 'a-ipath 1nap neto22 over "a path extending from ground, right-hand arniatureandfront contact'o'l '1'el"a y.516,'contact 534 and brush 531 of switch 'FS armature andback contact and-winding of 1nagnet522 to grounded battery. ldag'net 522.thereuponoperates and mores the brushes560 to .532 inclusive-of the switch FS one :step, whereupon the :operating circuit for the motor magnet 522 is interrupted. The switch FS isthus ready for thereception of the next-setiofiinpulses.

hen the counting relay '601 operated, lit completed a circuit'for J'DOtOIIDIQgIlCU 620 of counting switch GT over aipath extending from grounded hatter-y, winding, arinaturc and back contact 0fin'1agnet620, outer lefthand armature and back contact of relay 621, brush630and normal contact of switch GT back contact and lett hand armature of relay 622 and front contact and outer ll-glltlldlld armature of counting zrelay 601 to ground.

h Ia'gnet 6201 thereupon operates and moves the brushes 680 to 6533 ;inclusive .into engagement. with contacts 62% to 627 groundcd battery. disconnects the counting switch GT fl'OlU the receiving c1rcu1tR- :and places-the countr upon operates over a path extendin :t'roin grounded battery, winding and left-hand norlnal contacts-0t relay62l, brush631:and

contact 6250f switch Gil, and dront'contact and :left-ihand armature of counting relay 601 to .ground. Relay 1621 11H operating locks under control oi relay 662 and inattractingtits outer left-hand 1l111atL1lC,O] )1]S the operatlng' circuit dorinotorinagnet 620,

thereby bringing the brushes. of the switch :GT t0 rest. Counting relay 601 released when-relay 621 operated. Relay '621iniopcrating also completes a circuit for u'el-ay 622 over a path extending ulroin ground, front contact and right-hand armature 'O'lf relay 621 and winding of relay 622 to Relay 622 in operating ing switch Gil in operative relationship therewith.

At the outer right-hand arn'iature of :re-

lay 622 a circuit was extendeddor IHOtOI inclusive respectively. Relay 1621 thereswitch provides foritheproper SQQUQIIGZB OIE steps. Motor IIMIQHGUGGStllt-ZH operatedover circuit extending from ground, winding of "magnet 663, brush r611, a11d e0ntact 601,

vof switch SQ, outer riglit hand arn'iature and front contact of relay 622, conductor 698, segment 618, brush 619, and segment 6L7 of constantly operating'distributoiwD to ground when 1 brush 6.19 of v the distributor D passes over-segment 618 during rotation.

The ln-ushega611and 680-bit the switchSQ, are inovedone step due :to (1110111111)Ul$(3'=b6- ingconveyed to nragnet 663, whereupon a circuit for'pulsing relay 681 is completed over a vpathextending l roin grounded battery, winding-of rela-v 68:1, contacti627sa-nd brush 633 brush 6-80 oi switch. SQ; to 1-ground.

of switch GTF, contact 636 and Relay 681 -111 operating causes one impulse .torbe transmitted .over the impulse conductor 699 to :the pulsing relay 1700 lot the selector switch SL over a path. extending from vground, segment 61 7, brush 61-9 and.-seg1nent 681' of distributor :Dfirto conductor 690.

The operation of the system' for the remaining two digits of the: desired number will first be traced before :the .operation of the selector switch SL is described. As assumed, the next digit of the (lQSllQClTllllDlJBl? is 2. It will be noted that "HSISOOH rasithe three 900 cycle impulses were sentover'the line conductorsatothereceiving circuit PF,

that the :brush 191 of the distributor. D in rotating, again passes over the contact "192,

thereby completing a circuit for i and deliveringan impulse to motor niagnet-l02, which causes theimotor magnet102 to operatetand advance the brushes l tOhto 144C i nclusivegof Belay 681 releases when niotor 1na net66S 1- t v #3 again operates.

the switch SW one step into their fourth position.

In the fourth position of the brushes 140 to 144 inclusive of the sender switch SW, three closely succeeding impulses of 1100 cycle current will be sent over the line circuit to operate the frequency switch FS of the receiving circuit R due to the tens key 2 of the' sender S being depressed. Relay 540 of the frequency switchFS will be operated over a path extending from grounded battery, winding of relay 540, through the filter 500;, and thence over conductor 547 and the ring conductor of the line and cord circuit to conductor 149, and thence over brush 140 and contact 162 of sender switch SWV, left-hand contacts of tens key 2, brush 182 and contacts 170 of distributor D through the source 151 of 1100 cycle cur rent, through the right-hand contacts of tens key 2, contact 165 and brush 141 of.

sender switch SW, outer left-hand armature and front contact of relay 108, conductor 128, and thence over thepath previously traced including the tip conductor of the cord and line circuit to conductor 548, through the 1100 cycle filter 5007' to ground.

In response to each impulse transmitted relay 540, stepping magnet 542 will advance the brushes 550, 551 and 552 of frequency switch FS one step. Since for the digit 2 three impulses are transmitted to relay 540, the brushes 550, 551 and 552 will be moved into engagement with contacts 553, 554 and and right-hand normal contacts of relay 602, conductor 580, contact 555 and brush 552 of the frequency switch FS armature and back contact of relay 541 and back contact and right-hand armature of relay 586 to ground. Relay 586 is thereupon energized over a path extending from grounded battery, winding and left-hand normal contacts of relay 586, conductor 595 and front contact and outer right-hand armature of counting relay 602 to ground. Relay 586, in operating, locks up through its left-hand alternate contacts to ground at the contact 553 and brush 550 of switch FS to ground. As soon as relay 586 attracts its righthand armature a circuit is completed for stepping magnet 542 over a path extending from ground, right-hand" armature and front contact of relay. 586, contact 554 and brush 551 of frequency switch F8 armature, back contact and winding of magnet 542 to grounded battery, whereupon magnet 542 is operated and moves the brushes 550 to 552 of the switch F3 into engagement with the next set of terminals. The next termi nal with which brush 551 comes in contact is open, thereby causing magnet 542 to cease operating. The locking circuit of relay 586 is also opened at the next or normal contact whereupon relay 586 releases. The switch FS is then ready for the reception of the next set of impulses.

hen counting relay 602 operated it locked up temporarily under control ofrelay 641 and completed a circuit for motor magnet 640 of the counting switch CT over a path extending from grounded battery, winding, armature and back contact of magnet 640, outer left-hand armature and back contact of relay 641, brush 650 and normal contact of switch GT back contact and lefthand armature of relay 642, front contact and left-hand armature of relay 622, and front contact and outer right-hand armature of counting relay 602 to ground. 1

Under the control of magnet 640 the brushes 650 to 653 inclusive of the counting switch GT will be moved over their associated contacts until the terminals of the switch GT corresponding to the operated hand armature of relay 602 to ground. Rei lay 641, in operating opens the locking circult for counting relay 602, and at its outer left-hand armature, the operating circuit for magnet 640, whereupon said magnet ceases,

operating,and closes at its right-hand armature, an obvious circuit for relay 642. Relay 641, in operating, locks through its lefthand alternate contacts to ground through the back contact and armature of relay 662. Relay 642, in operating, connects the counting relays in operative relationship with the brushes 680 and 611 one step. Relay 682 will then be operated over a path extending from grounded battery, winding of relay Oil nm m- 682, contact 647 and brush 653 of counting.

switch GT contact 637 and brush 680 of the sequence switch SQto ground. Relay .682, in operating, will cause two impulses to be delivered to the impulse conductor 699 over apath extending from ground, segment 61?, brush 619, segments 681" and 682 to the impulse conductor 609.

When the brushes of the. sender switch SlV are moved into their fifth positions, due to magnet 102 operating after the second set of impulses have been delivered from the distributor D two impulsesof 1100 cycle current and one impulse of 1800 cycle current will be sent over the line to their respective frequency filters in the receiving circuit R due to the depression of the units key 0. Relay 540 of the frequency switch 500i will be energized twice over a path extending from grounded battery, winding of relay 54.0 through the frequency filter 5007, and thence over condnctor547 and the patl'r previously traced to conductor 149, and thence throu'gl'rbrush 140 and contact 1680f sender switch SW left-hand contacts of units key 0, brush 190 and contacts 172 of sender switch SlV, through the source 151 of 1100 cycle current, inner right-hand contactsof units lrey 0, contact 166 anchbrush 14 1 of send or switch SW through the outer left-hand armature and front contact of relay 108, and thence over the path previously traced ineluding conductors 128 and 548, and frequency filter 5007 to ground.

In response to the two impulses trans mitted to relay 540, magnet 542 will be operatied twice to move the brushes 550 to 552 inclusive of the frequency switch F S into engagement with contacts 556 to 558 inclusive respectively. Slow to release relay 541 is energized as previously described on the first impulse being transmitted to relay 540 and deenergizes after the last impulse has been transmitted to said relay 540. Relay 541, in retracting its armature, completes a circuit for relay 511 over a path extending from ground, right-hand armature and back contact of relay 586, back contact and armature of relay 541, brush 552 and contact 558 of frequency switch FS wind ing and right-hand normal contacts of relay 511 and back contact and inner righthand armature of relay 500 to grounded battery. I

Closely succeeding the. twoimpulsesv of 1100 cycle current transmitted to the receiving circuit- R one impulse of 1300 cycle current will be transmitted from the source 152, through the contact 171 and brush 190, of the distributor D and thence over a path previously traced to relay 560 of the frequency switch FS In responseto the impulse transmitted relay 560, relay 56-1 and magnet will be energized over obvious circuits. Magnet 562,v in operating,

moves the brpshes 570, 571 and 572 of: thefrequency switch FS into engagement With-- the contacts 573, 574 and 575 thereof, respectively.

a circuit is thereupon completed for relay;

508* over a path. extending from ground,

Relay 561deenergizes soon after the impulse is transmitted torelay 560 and trol of relay 661 and completes a circuit forv the operation of elays 581 and 586 of the switches FS" and Fsfli'espectively, over a path extending from ground, outer rightha'nd armature and front contact o f relay 610, conductor. 595,and thence in parallel through the left-handnormal contacts and windings of relays581 and 586 to grounded battery. Relay 516 is operated. at this time but is not lockedup. Relays 581 and .586,

in operating, lock and complete-circuits for motor magnets 562 and 542, respectively,

similar to those traced for the motor magnet 522 of the switch FS whereupon the brushes of the switches FSt-and. FS, are.

stepped to a normal position. Relays581' and thereupon retract-their armatures. Relay 610, in operating, completes a circuit for motor magnet 6600f the switch GT over a path extending from grounded battery, winding, armature and baclr contact of magnet 660, outer left-hand armature and back contact of relay 661, brush 670 and normal contact of switch GT front contact and left-hand armature of relay 642, front contact and left-hand armature of relay 622,

and front contact and outer right-hand armature of relay 610 to ground. Under the control of magnet 660the brushes 670 to 673 inclusive are moved over their associated terminals until the terminals corresponding to the operated counting relay are reached, whereupon relay 661 operates 'overa path extending from grounded battery, winding and inner left-hand normal contacts of res lay 661, brush 671and contact665 of switch GT and front contactand left-hand armature of relay 610 to ground. Relay 661, in operating, locks throughits left-hand alternate contacts to ground through the back contact and armature of relay .662, Atthe outer left-hand armature of relay 661 the circuit for the motor magnet 660 is interrupted.

vIn attracting its right-hand armature relay 661 prepares a circuit for the motor magnet 6.63 over a path extending from grounded battery, winding of: magnet 663, brush 611 and-contact 693 of switch SQ,

ftront contact and right-hand armature of relay 661 to segment 618 of the distributor D The arm 619 of the distributor D in rotating, will extend ground from the segment 617 through the arm 619 to the segment 618, whereupon magnet 663 will energize and will step the brushes 680 and 611 of the switch SQ, into the next position. Relay 690 will thereuponbe energized over .a path extending "from grounded battery,

tact 694 and brush 611 of the sequence switch SQ, winding ofmotor magnet 663 to grounded battery. Magnet 663, in operating, moves the brushes 6S0 and611 of the switch SQ, into their iifth positions, whereupon rclay 662 is energized over a path" extending from ground, brush 680 of switch SQ, and its fifth contact, and winding of relay 662 to grounded battery. Magnet 663 again operates over an obvious circuit and moves the brushes 680 and-6'11 to their sixth position which is a normal position. Relay 662 operates in the fifth position of brush 680 and at its arnigature and back contact opens the holding circuits for relays 621, 641 and 661 of the counting switches GT GT and CT, respectively; Relays 621, 641 and 661 thereupon release. Under the control of their respective motor magnets the switches GT GT and CT are then restored to normal position. Switch CT? is restored to normal due to magnet 620 operating over a path including winding, armature and back contact of magnet 620, outer left-hand contacts o1 relay 621 brush 630 and upper contacts of switch GT and, the left-hand normal contacts of the "counting relays. Switches GT and are restored in a similar manner. Relay 662 in operating removes ground troni the brush 461 of the finder switch RS1 so that relay 414 releases.

Relay 414, in retracting its left-hand armature causes the release of relay 409 and in retracting its right-hand ari'i'iature opens the holding circuit for relays 411 and 412, whereupon said relays. 411 and 412 release. Relay411, in releasing, completes a circuit for relay 410 over a pathextending from grounded battery, righthand armature and back contact of relay 411, winding of relay 410, brush 462, and contact 467 of switch RSF, and back contact and outer right-hand armature o't relay408 to ground. Relay 410 thereupon operates and completes a circuit for motor magnet 401 over a path extending fromgrounded battery, winding armature and back contact of magnet 401, armature andtront contact of relay 410, brush 463 and contact 469 of switch RFS, and back contact and inner right-hand armature of relay 408 to ground. Magnet 401 thereupon operates and advances the brushes of the switch BSF one step. Ground will be present upongthe next contact and all succeeding contacts with which brush 463 engages due to conductors (not shown) leading from such contacts to contacts of relays similar to relay 408, so that the brushes of the switch RSF will be restored to normal in the well known manner whereupon relay 410 releases and magnet 401 ceases stepping. q

After the last impulse of 1300 cycle current for the digit 0 has been delivered to the line circuit, the cord selector switch CS 01? the cord circuitwill be restored dueto a.

circuit being completed for motor magnet 102 over a path extending "from ground, con tact 192 and brush 191 of distributor D, outer right-hand contacts of units key 0, the strapped contacts associated with brush 142 of the switch 51V, brush 142, and winding of magnet 102 to grounded battery. The constantly rotating brush 191 in passing over contact 192, operates'magnet 102 over this circuit and moves the brushes of switch S16 until a circuit for-the key release magnet 118, is completed over a path extending from ground, winding of relay 1,18, contact 167, and brush of switch SlV, brush 123 and contact 133 of switch CS and winding oi relay 107 to grounded battery. Relay 118, in operating, restores the depressed sender keys 1., 2 and 0 to normal, and ground being connectedto the last two contacts of the bank associated with arm 142, switch 81V advances to normal thereby opening the operating circuit for magnet 102, whereupon the switch S16 is, ready for the next call. Relay 107 is also energized in thecircuit just traced and locks up through its lefthand alternate contacts to ground through the front contact and armature of relay 101. Relay 107, in operating, also opens at its left-hand armature and back contact the circuit for relay 105, whereupon said relay 105 releases. In attracting its right-hand armature, relay 107 opens the locking circuit for relay 108, whereupon relay 108 releases. Relay 108, in retracting its armatures, coniple-tes a circuit for relay 106 over a path extending from grounded battery, inner lefthandarmature and back contact 01 relay [108, winding of relay106, brush 125 and loo found.

contact 135 of switch CS and front contact and right-hand armature of relay 107 to ground. Relay 106, in operating, completes a circuit for magnet 126 over a path extending from grounded battery, winding, armature and back contact of magnet 12%, righthand'armature and front contact of relay 106, brush 125 and contact 135 of switch CS, and front contact and right-hand armature of relay 107 to ground. Magnet 126 therefore operates and moves the bros-shes 120 to 125 inclusive into their normal 7 positions whereupon relay 100 releases and the motor magnet 126 ceases stepping.

Referring now to the operation. of the switches controlled over the impulse conductor 699, it will be noted that each time the conductor 699 is grounded relay 700 will be energized over a path extending from ground on conductor 699, brush 443 and contact 41-7 of switch RQF, front contact and outer right-hand armature of relay 4-12, and winding of relay 700 to grounded buttery.

In attracting its left-hand armature, relay 700 completes a circuit for slow-to-release relay 712 and motor magnet 713 ovc'r a path extending from ground. left-hand armature and front contact of relay 700, winding of relay 712, winding of magnet 713, first contact of side switch arm 714-, and arm 714 to grounded battery. Relay 712 is thereupon energized and completes an obvious circuit for side switch magnet 731. In response to each impulse transmitted to primary magnet 713, the brushes of the selector switch SL are moved one step in a primary direction. After each impulse has been transmitted to relay 700, it releases its arn'iatures, thereby opening the circuit for slow-to-release relay 712. Relay 712 is so designed, however, that it retains its armature attracted during the transmission of a series of impulses and releases its armature at the end of the series of impulses. Relay 712 in retracting its armature, opens the circuit for side switch magnet 731, whereupon said magnet causes the side switch arms 71% to 718 inclusive to be moved into their second positions in the well known manner. At side switch arm 717 a circuit is completed for side switch magnet 731 over a path extendingfrom ground, secondary oft-normal contacts 7 89, side switch arm 717 and its second contact and winding of side switch i'i'iaguet 7 31 to grounded battery. An obvious selfinterrupting circuit is also completed in the second position of the side switch arm 714. for secondary magnet 722.

Under the control of magnet 722, the brushes 7 10, 741-1 and 7 12 of the selector switch SL are moved over their associated contacts until an idle connector switch is The test contact of an idle connector switch will have no potential thereon. The test contact of a busy connector switch will have ground potential thereon, so that sidev switch. magnet-731 will remain energized over a path extending from grounded battery, winding of magnet 731, second contact of side switch. arm 717 and arm 717, and

brush 742 to round as lon as brush o a a:

encounters busy connectors. As soon as an ldle connector is reached, side switch magnet 731 will deenergize, thereby moving the brushes 71-1- to 718 inclusive into their third positions.

Assuming that connector CC is the one to which the connection has been extended, relays 800 and 801 of connector switch CC will then be energized over a path extending from grounded battery, winding of relay 800, back. contact and outer left-hand armature of relay 860, conductor 851 terminal 74 1, brush 74-1, of switch SL, side switch arm 716 and its third contact, back and back contact of relay 860 and windingof relay 801 to ground. Relay 801 in operating completes an'obvious circuit for relay 802 which is preferably of the slow to release type, Relay 802 in operating locks to ground at the third contact side switch arm 717. Relay 701 will also be energized in the circuit just traced. i

In response to the next set of impulses transmitted over the impulse conductor 699, relay 700'will be energized twice, thereby causing two interruptionsin the circuit of the relays 701, 800 and 801, whereupon these relays retract their armatures a number of times corresponding to the interruptions in the circuit of these relays. Primary magnet 810 ofthe connector switch CC-is energized each time the relay 800 retracts its armature over a path extending from ground, armature and back contact of relay 800, right-hand armature and front contact of slow-to-release relay 802, winding of slow-to-release relay 803, back contact and outer armature of relay 804, winding of magnet 810 and first contact of side switch arm 831 and side switch arm 831 to grounded battery. Relay 803 is energizedupon the first impulse of current theretln'migh and in attracting its arn'iature completes a circuit for side switch magnet 805 over a path extending from ground, armature and front contact of relay 803 and winding of side switch'magnet 805 to grounded battery. Magnet 805 in attracting itsarmature disconnects relay 835 from the test brush 822 and the side switch arm 830. Relay 803 is preferably of the slow-to-i'elease typeand retains its armature attracted duringthe had transmission of a set of impulses, but releases its armature after the last impulse of a series.

As soon as the first set of impulses has been transmitted to the connector switch CC, relays 701, 800 and 801 again attract their armature for a short interval, thereby interrupting the circuit for relay 803. Relay 803 thereupon retracts its armature, thereby opening the circuit for side switch magnet 805, whereupon said magnet causes the movement of the side switch brushes 830 l and 831 into their second positions.

In response to the next set of impulses, the circuit of relay 800 willl be interrupted ten times, whereupon ten impulses will be delivered to the secondary magnet 811 over a path extending from ground, armature and back contact of relay 800, right-hand armature and front contact of relay 802, winding of relay 803, back contact and armature of relay 804, winding of secondary magnet 811, second contact of sFde switch arm 831 and side switch arm 831 to grounded battery. In response to the actuations of secondary magnet 811, the brushes 820 to 822 will be moved ten steps over their associated contacts into engagement with the terminals of the desiredline. Relay 803 will be energized upon the first impulse and will remain energized until after the last impulse has been delivered to the secondary magnet 811, whereupon said relay 803 will retract its armature thereby opening the operating circuit for side switch magnet 805.

Assuming that the called line is idle, side switch magnet 805 will retract its armature, due to the absence of ground potential on test terminal 825, thereby moving the side switch arms 830 and 831 of switch CC into their third positions. Relay 835 of the connector CC and cut off relay 826 of the called line will then be energized over obvious cir cuits due to ground being connected to the third position of the side switch arm 830. Relay 835, in attracting its armatures, extends the conductors 840 and 841 through to the terminals 823 and 824, respectively.

of the called line. The cut off relay 826 of the called line performs the well-known function of preventing the non-numerical switch at the called station from operating when the called station removes the receiver from the switch hook.

When the last set of impulses has been delivered to the connector switch, the brushes thereof will be in engagement with the terminals of the desired line and as heretofore described relay 412 will release and relays 701, 800 and 801 will again energize. Relay 704 will then energize over a path extending from grounded battery, right'hand armature and back contact of relay 711, winding of relay 704, front contact and armature of relay 701, side switch arm 718 and its third contact, and left hand armature and back contact of relay 412. Relay 704 in operating completes a circuit for relay 705 through its outer left hand contacts and a circuit for relay 720 through its inner right provided at her position which will be actuated in the manner hereafter described. Relays 307 and 416 operate when the constantly rotating distributor D reaches the contacts with which the leads from these relays are connected. The circuit for these relays may be traced as follows: grounded battery, winding of relay 307, brush 344 and contact 364, of distributor D outer lefthand armature and back contact of relay 3113, contact 373 and brush 333 of switch LFS, left-hand normal contacts and winding of relay 416, and front contact and lefthand armature of relay 720 to ground. Relay 416 looks up tei'nporarily over a path extending from grounded battery, inner right-hand armature and back contact of relay 428, left-hand alternate contacts and winding of relay 416, and front contact and left-hand armature of relay 720 to ground. During the next cycle of the distributor D relay 428 is operated over a path extending from ground, left-hand armature and front contact of relay 720, front contact and right-hand armature of relay 416, winding and left-hand normal contacts of relay 428, brush 333 and contact 373 of switch LFS, back contact and outer left-hand armature of relay 313, contact 364, and brush 344 of distributor D and winding of relay 307 to grounded battery. Relay 428, in operating locks up momentarily under control of relay 720, releases relays 416 and 720 and also completes a circuit for relay 711 and 723 over a path extending from ground, outer right-hand armature and front contact of relay 428, thence in parallel thru the lefthand normal contacts and winding of relay 711 to grounded battery and the left hand normal contacts and winding of relay 723 to grounded battery. Relay 711 thereupon operates and locks up through its left-hand alternate contacts the intermediate righthand armature and back contact of relay 720, the front contact and armature of relay 701, side switch arm 718 and its third contact to ground at the back contact and left-hand armature of relay 412. Relay 711,

llhi 

